Bulk containers, often referred to as "flexible intermediate bulk containers" or "FIBCs", are used in the lifting, transportation and storage of bulk materials in powder, granular, flake or other particulate forms. Typically, these bulk containers hold large quantities of these materials, of up to one tonne or more, and are in the form of large bags or sacks made of a flexible woven fabric, such as woven polypropylene or other suitable synthetic materials.
In order to be able to lift and transport the bulk container, lifting loops or lifting straps are associated with the bulk container, typically at an upper edge thereof, so that the bulk container may be transported in an upright position to inhibit spillage of the bulk material from the container. These lifting straps are designed to cooperate with the forks of a forklift, a hook or other lifting device or member such that the forks of the forklift may be accepted or received therein. Broadly speaking, these lifting straps are either integrally formed out of the side wall of the bulk container from the material comprising the bulk container or affixed or fastened in some manner to the side wall of the bulk container. Most commonly, these lifting straps are stitched to the side wall of the bulk container adjacent the upper edge thereof. Further, these lifting straps are typically formed of high strength or high density webbing which is closely woven or braided.
Previously, these lifting straps were required to be manually lifted and placed on the lifting member, i.e. the forks of the forklift. However, more recently, various rigid, semi-rigid and flexible lifting straps have been designed which remain in an upstanding position such that the lifting member may be more readily accepted in the loop formed by the lifting straps in one operation without manual assistance.
U.S. Pat. No. 5,161,853 issued Nov. 10, 1992 to Polett and U.S. Pat. No. 4,499,599 issued Feb. 12, 1985 to Polett et al describe the use of a relatively rigid "tubular member", constructed from rubber, synthetic plastic or like materials. The tubular member encloses or encases the lifting strap to provide support and to maintain the strap in an upstanding position. The tubular member is a separate or distinct element or component apart from the lifting strap and must be assembled onto the strap during the manufacture of the bulk container.
U.S. Pat. No. 4,300,608 issued Nov. 17, 1981 to Cuthbertson describes lifting straps which include "resilient means" such as "an elongated resilient insert" which is incorporated into the lifting strap for forcing the loop formed by the strap into an upstanding position. This elongated resilient insert may take a variety of forms, such as a strip of a resilient plastic or a metallic material inserted into the strap, a plastic or wire material woven into the strap or impregnation of the strap with a plastic material.
U.S. Pat. No. 4,822,179 issued Apr. 18, 1989 to Nattrass describes a lifting strap which is made to be stiffer than a conventional lifting strap by forming it of at least three superimposed layers of material folded and sewn together. This multi-ply construction provides a degree of stiffness to the lifting strap. Further, the multi-ply lifting strap may be twisted 180.degree. to provide added rigidity to the loop formed by the lifting strap.
Each of these upstanding lifting straps requires either the use of additional materials in the form of plastic, metal or rubber tubing, inserts or impregnation or the use of an excessively large amount of the lifting strap material to urge the strap to an upstanding position. In either event, the requirement for these materials, and the associated labor expenses for the assembly or manufacture of these lifting straps, tends to increase the overall costs associated with their production.
There is therefore a need in the industry for an upstanding lifting strap, for use in association with a bulk container, which is relatively inexpensive and which is relatively cost effective to produce as compared to known upstanding lifting straps. Further, there is a need for a bulk container having such a lifting strap and a method for producing it.